wiggle room       
noun [ U ] uk/ˈwɪɡ.əl ˌruːm/ us/ˈwɪɡ.əl ˌruːm/ (mainly UK also wriggle room)
 informal回旋余地 
the freedom or opportunity to do something, or to change your mind and do something differently if that is what is needed
  We need to leave ourselves some wiggle room when we're negotiating the deal. 我们谈判业务的时候需要给自己留一些回旋余地。